1. Field of the Invention
This invention relates to internal antennas for hand-held mobile telephones and wireless communication devices. More particularly, the present invention relates to a switch contact for connecting a planar inverted F antenna in the device to a printed circuit board therein.
2. Description of the Related Art
Internal antennas for wireless communication devices are becoming more popular due to their ease of integration into the housing of the device, lower cost, and smaller profile. A popular internal antenna is the planar inverted F antenna (PIFA). A major difficulty encountered in mass production of a PIFA is the method used to inexpensively provide a connection between the signal on the printed circuit board (PCB) to the feed point on the PIFA. The simplest method is to insert spring contacts that apply pressure between the PCB and the PIFA. The proper amount of pressure is crucial for making a consistent, reliable electrical connection.
Spring contacts of the type described above may be configured in different ways. One way is to use what is called a xe2x80x9cpogoxe2x80x9d pin. The pogo pin is made of a spring housed inside two closed end concentric tubes. The spring provides pressure to the tubes to press against both the PCB and the PIFA. The tubes hold the spring, provide an electrical path, and enclose the spring to eliminate the inductance of the spring. However, pogo pins are usually too expensive for use in mass production.
Another method of configuring the spring contact is to form metal strips into beams that perform all the functions mentioned hereinabove. The beams are necessary to prevent deformation of the metal strips due to flexing the metal during switching. Deformation reduces the spring force of the metal. Unfortunately, the spring portion of the contact is not enclosed to eliminate the induction. In most cases, the additional induction causes the electrical size of the PIFA to be smaller to compensate for the inductance. Smaller electrical size in general means the gain will be lower.
A switch contact is disclosed for a wireless communication device including a printed circuit board having a planar inverted F antenna arranged parallel thereto and spaced therefrom. For purposes of description, the printed circuit board will be described as being positioned below the planar inverted F antenna. The spring contact is generally U-shaped and is positioned between the printed circuit board and the planar inverted F antenna in a compressed state for electrically connecting the printed circuit board to a feed point on the planar inverted F antenna. The spring contact includes a base portion having spaced-apart first and second leg portions extending therefrom. The first leg portion of the spring contact curves laterally and upwardly from the PCB, bends 180 degrees over a relatively large radius (base portion), with the second leg portion curving laterally and upwardly to the PIFA. The first leg portion is in electrical contact with the printed circuit board with the second leg portion being in electrical contact with the feed point on the planar inverted F antenna. The spring contact forms the mechanical portion of the contact that provides upward and downward spring force to ensure good electrical connection between the surface of the PIFA and the contact. The first leg portion has a first spring extension extending therefrom towards the printed circuit board while the second leg portion has a second spring extension extending therefrom towards the planar inverted F antenna. The first and second spring extensions are biased towards one another so that the spring extensions are in electrical contact with one another. The spring extensions provide an electrical path that bypasses the inductive path of the spring portion of the contacts. The inductance of the spring is short-circuited by the bypass.
The distance between the PCB and the PIFA has a dimensional tolerance which must be included in the overlap between the spring extensions and the lateral spring forces. The overlap between the extensions compensates for dimensional tolerance stack-up.
The spring contact of this invention may be used in other types of antennas such as microstrip patch antennas.
It is therefore a principal object of the invention to provide an improved switch contact for a wireless communication device including a printed circuit board and a planar inverted F antenna arranged parallel to the printed circuit board and spaced therefrom.
Yet another object of the invention is to provide a switch contact of the type described which include spring extensions at the ends thereof which provide an electrical path that bypasses the inductive path of the spring portion of the contact.
Yet another object of the invention is to provide a switch contact for a wireless communication device which has the ability to compensate for dimensional tolerance stack-up.
These and other objects will be apparent to those skilled in the art.